2- Color and Shade Matching in Restorative Dentistry.pptx

Color and Shade Matching in Restorative Dentistry: Part 2 Colour-related Properties of Restorative Materials  Restorative materials should display colour and optical properties similar to those of dentin and enamel.  Compatibility:  When choosing dental materials such as composite...

Color and Shade Matching in Restorative Dentistry: Part 2 Colour-related Properties of Restorative Materials  Restorative materials should display colour and optical properties similar to those of dentin and enamel.  Compatibility:  When choosing dental materials such as composite resins or dental ceramics for restorative procedures, the shade selection of the material will be dependent on the brand or system in use.  A material will be most compatible with a tooth when it has shades that mimic both dentin and enamel.  Stability  The colour stability of dental materials is a significant concern for colour and appearance in restorative dentistry.  When comparing composite resins and dental ceramics ,resins are less colour stable after aging.  Interactions  An existing colour difference between the restorative material and the tooth can be lessened with favourable colour interaction properties, such as layering and blending. Colour-matching Tools—Dental Shade Guides  Dental Shade Guides:  Dental shade guides are tab-based tools fabricated from ceramic, resin or some other form of plastic or acrylic material.  The shade tabs are typically arranged according to some dimension of colour,  but because of the complex polychromatic nature of natural teeth, a given shade guide system will only serve as a guide and not as an exact colour matcher. Commercial Shade Guides  Ceramic Based  For direct restorative procedures, there are many shortcomings associated with the use of a ceramic- based tooth shade guide for dental shade matching,  but it is the most logical starting point for shade matching as most composite resins are keyed to a commercially available ceramic-based system.  1- Vita classical A1–D4 shade guide (VITA Zahnfabrik)  Most popular ceramic-based shade guide.  Each tab has a number and a letter. According to the manufacturer, the letters represent one of the following hue groups:  A = reddish-brown  B = reddish-yellow  C = grey  D = reddish-grey  The number next to the letter on the tab label represents the chroma and value within each of the A–D  groups: 1 = lowest chroma, lightest  and 4 = highest chroma, darkest.  Within this system, shade B1 is the least chromatic and lightest of the reddish-yellow shades, whereas B4 is the most chromatic and darkest of the reddish- yellow shades.  One way to use this shade guide is to observe the most chromatic portion of the patient’s tooth, usually the cervical region of the canine and select the best hue group.  Next, the best shade within that hue group should be selected based on the closest chroma number.  Vita 3D-Master shade guide (VITA Zahnfabrik):  VITA released a shade guide in 2007 specifically designed for bleach monitoring—Vita Bleached guide 3DMaster  Including very light shades that enable monitoring of whitening efficacy of initially light teeth (e.g. shade B1 before bleaching).  This scale includes 29 shades (15 tabs with 14 interpolations) with colour evenly distributed between tabs.  II. Vita Toothguide 3D-Master.  III. Vita Linearguide 3D-Master Vita Linearguide 3D-Master. Primary division into groups is made according to value (0–5); within the groups the chroma (1 = least and 3 = most) and hue (M = neutral middle hue; L = less red and R = more red) vary.  A major concern with using the ceramic-based shade Guides is that the actual composite shade may or may not match the original classical tabs.  If a restorative system is not supplied with a shade guide, then using a ceramic shade guide may be used as a starting reference  Polymer Resin Based  Proprietary shade guides supplied with a restorative composite resin system are often fabricated using the same restorative material.  In other words, they are resin-based tooth shade guides.  Initially, this is a good option because they will have the same optical properties as the restorative material.  However, colour stability of the tabs may become problematic over time as the tabs are disinfected and get darker.  Other Materials (Plastics/Acrylics)  Custom Shade Guides  Depending on the accuracy of the shade guide supplied with the system, it may be more accurate to use the actual composite cured on the tooth. Colour-matching Instruments  Various devices have been used in dentistry, including digital cameras, scanners, spectrophotometers and colorimeters.  The one instrument that has remained on the market over many generations is the Easyshade device manufactured by VITA.  The latest generation of this spectrophotometer is the Vita Easyshade V.  While colour measuring instruments continue to improve, they still do not replace the operator. Dental Photography  Digital single-lens reflex (DSLR, recommended) cameras, portable cameras and cell phones are used for digital photography.  A DSLR camera can be used with a general-purpose lens or dedicated macro lens, and a variety of flashes: single-point, ring, dual-point and twin tube flash.  Mirrors and retractors are important accessories for digital photography.  Digital photography is frequently used in conjunction with general software programs (such as Adobe Photoshop and Corel Photo-Paint).  Mobile apps are becoming increasingly popular for colour management. Visual Shade-matching Method  Color matching is dependent on controlling subjective variables such as color vision deficiencies and eye fatigue, while at the same time controlling the proper viewing conditions and selecting the correct light sources.  The following order of three preshade-matching steps and five shade-matching steps will provide a predictable method for visual shade matching.  Three Preshade-matching Steps:  Step 1: Check Colour Vision  Test for colour discrimination competency in dentistry consists of creating pairs of shade tabs from two identical shade guides (at least one set should not have original markings, such as A1–D4 of classical, visible)  Step 2: Use Colour Corrected Lighting:  The way we perceive colour is greatly influenced by the light source used to illuminate the object.  In shade matching, we want to use an illuminant which best matches the white light of natural daylight.  Step 3: Control Surround/Viewing Conditions  the surrounding conditions can change the overall colour perception of an object.  Start by placing a neutral colour patient napkin over sparkling jewellery or bright clothes and having the patient remove reflective glasses and coloured lipstick.  Five Shade-matching Steps  Once the preshade-matching steps have been addressed, the following shade-matching steps can be implemented to further improve visual shade- matching performance.  Step 1. Perform at the Beginning  Performing shade matching at the start of the appointment will also help prevent eye fatigue and strain on the visual system as time progresses.  Tooth dehydration occurs during restorative field isolation and alters the tooth colour.  As teeth dehydrate, they will appear lighter, less chromatic and more opaque.  Step 2. Set Light and Observer  Shade matching should be performed at the distance of 25–35 cm (10–14 in.), with tooth being observed perpendicularly to its labial surface and with the 45-degree angle of illumination.  The viewer’s eyes should be on the same level as the shade  Step 3. Use Appropriate Technique  The shade-matching technique includes selection of the appropriate shade guide for the task, appropriate shade tab positioning, technique and duration.  The ideal position of the tab is on the same plane and the same vertical (cervical to incisal) orientation (Fig. 17.25).  the shade tab can be placed in between upper and lower teeth, vertically or horizontally (Fig. 17.25) to the longitudinal axes of the natural teeth.  Macro-Mini-Micro Shade-matching Technique  Macro-phase  Shade matching typically begins with a quick glance and selection of potentially adequate tabs.  The entire shade guide is used, positioned close to the tooth whose colour is being matched, and moved laterally to facilitate this selection (Fig. 17.28A).  Mini-phase  After this, the potentially adequate tabs are clustered together (in or outside the shade guide holder), and the best matches for incisal, middle and cervical third are identified (Fig. 17.28B).  Once the best match or matches have been selected in the final micro-phase, one needs to determine and describe differences in hue, value and chroma between the regions of natural tooth and selected shades.  A key to discerning the difference in shade between two colours, especially if the colour difference is small, is to use very short glances for visual shade matching.  It is not advisable to stare at any colour during shade matching.  Staring at blue for example will create the illusion that the teeth are more yellow than they actually are in reality.  It is preferable to see the true colour, not a complementary afterimage.  To avoid staring at the target, it is best to gaze at a neutral gray card in between shade-matching trials.  Ideally the glances at the target shade should last only between 5 and 7 s.  Step 4. Communicate  The next step in the shade-matching process is to capture, record and communicate the selected tooth shades.  The shades observed for direct restorations should be mapped out to assist in material selection during the restorative procedure.  Step 5. Verify  The final step is to verify the colour of restoration (direct/ indirect) visually, using several different lights, shade matching distances, observation angles and/or observers.  For direct composite resin restorations, the verification step can be made with a mock-up restoration or by simply applying (and light-curing) a small increment of the selected composite material to the area(s) of the tooth corresponding to the